Cathode-ray tube

ABSTRACT

A cathode-ray tube whose screen is essentially a semiconductor quantum generator formed by an optical resonator and an active medium placed therein. The active medium is a film of semiconductor material deposited on a substrate and capable of induced light emission and amplification at the density of electrons in the beam sufficient to bring about an inversion of energy levels in the semiconductor film. One of the reflecting surfaces of the optical resonator is the surface of the film exposed to the electron beam inside of the tube envelope.

United States Patent Nikolai Gennadievich Basov;

Oleg Vladimirovich Bogdankevich, Moscow; Alexandr Sergeevich Nasibov, Krasnaya Pakhra, Moscous Oblast,

Inventors U.S.S.R. Appl. No. 706,877 Filed Feb. 20, 1968 Patented Jan. 26, 1971 Assignee Fizichesky lnstitut lmeni Lebedeva Moscow, U.S.S.R. Leninsky prospekt Priority Feb. 20, 1967 U.S.S.R. 1,135,916

CATl-IODE-RAY TUBE 11 Claims, 3 Drawing Figs.

US. Cl 313/92, 313/108 Int. Cl H01] 29/18 Field of Search 313/108D,

[56] References Cited UNITED STATES PATENTS 2,965,783 12/1960 313/108 2,992,349 7/1961 313/92 3,243,625 3/1966 313/92 3,305,685 2/1967 Wano 313/108 3,339,016 8/1967 Merryman 3 l 3/92X Primary ExaminerRodney D. Bennett, J r. Assistant Examiner-Joseph G. Baxter Attorney-Waters, Roditi, Schwartz and Nissen ABSTRACT: A cathode-ray tube whose screen is essentially a semiconductor quantum generator formed by an optical resonator and an active medium placed therein. The active medium is a film of semiconductor material deposited on a substrate and capable of induced light emission and amplification at the density of electrons in the beam sufficient to bring about an inversion of energy levels in the semiconductor film. One of the reflecting surfaces of the optical resonator is the surface of the film exposed to the electron beam inside of the tube envelope.

CATI-IODE-RAY TUBE The present invention relates to electronic devices, and more specifically to cathode-ray tubes and to television such as, for example color television and Oscilloscopes and computers and such.

There exists a well-known type of cathode-ray tube which is essentially an evacuated envelope housing an electron gun. The electron beam from the gun is directed by a control system, which may be a magnetic one, onto a phosphor-coated screen where the energy of electrons is converted to light energy.

One of the disadvantages of such cathode-ray tubes consists in that their luminance is limited by the diffusive divergence of the radiation emitted by eachluminous point of the screen. This, in turn, necessitates the use .of high-speed optical systems for further transmission of the picture.

An object of this invention is to eliminate the above-mentioned disadvantage and to provide for the high luminance of the screen, both total and spectral.

This and other objects are accomplished by providing a cathode-ray tube whose screen, where the energy of electrons is converted to light energy, is essentially a semiconductor quantum generator formed by an optical resonator and an active medium placed therein, said active medium being in fact a film of semiconductor material deposited on a substrate and capable of induced light emission and amplification at the density if electrons in the beam sufficient to bring about an inversion of energy levels in said semiconductor film, one of the reflecting surfaces of the optical resonator being the surface of I said film exposed to the electron beam inside the tube envelope.

The substrate of the semiconductor film may be made optically transparent. Then the resonator will be formed bythe film surface exposed to the electron beam and the substrate surface outside the envelope.

If the divergence of light from the screen is to be reduced, the length of the resonator should be increased, for which purpose it is preferable that the resonator be formed by the film surface exposed to the electron beam and a reflector placed some distance from the substrate outside the tube envelope.

In order to simplify the design of the screen, it is preferable to make the semiconductor film and the substrate into a planeparallel plate. 1

Depending on the desired color of the picture, the film may be made of any one of the following semiconductor materials: gallium arsenide for infrared; gallium arseno-phosphide for red-yellow; zinc selenide for blue; cadmium selenide for orange; cadmium sulfide for green; and zinc sulfide for ultraviolet light.

In some cases, for example in color television, the semiconductor film may be formed by dots of different semiconductor materials, thereby producing a color mosaic.

A cathode-ray tube with a screen made as just described provides for high luminance owing to provision of a resonator. Thus, while existing cathode-ray tubes radiate within an angle of 2 radian, in the tube of the herein proposed design the divergence angle is reduced to 25, with an accompanying gain of to 10 times in the intensity of the luminous flux.

The invention will become more fully understood from the following description of preferred embodiments when read in connection with the accompanying drawings, wherein:

FIG. 1 shows a cathode-ray tube according to the invention, whose screen has a semiconductor film in the form of a planeparallel plate;

FIG. 2 is a sketch of a cathode-ray tube whose resonator is formed by the reflecting surfaces of the film and the substrate; and

FIG. 3 shows the mosaic screen of the cathode-ray tube.

Referring to FIG. I, the cathode-ray tube has an evacuated envelope 1 which holds an electron gun 2 and a deflectional system 3 for control of the electron beam 4. The CRT screen has a plane-parallel plate 5 made from a film of a semiconductor material deposited on a substrate 6; The film surface 7 exposed to the electron beam 4 and the surface 8 of the plate 5 are made reflecting and from, between themselves, an optical resonator, while the semiconductor film is an active medium capable of induced lightcmission when excited by electrons. Thus, the resonator and the plate 5 make up a semiconductor laser.

Emission from the CRT screen may be obtained in both the forward and the reverse direction relative to the direction of the electron beam. lnthe former case the substrate should be fabricated from a material transparent to the generated emission. FIG. 2 illustrates the former case, and FIG. 1, the latter.

The semiconductor film may be made from any semiconductor material capable of induced light emission and amplification when excited by electrons, such as gallium arsenide, gallium arseno-phosphide, zinc selenide, cadmium selenide, cadmium sulfide and zinc sulfide.

The operation of the cathode-ray tube provided by the invention is as follows.

A pencil beam 4 of electrons with an energy and density suf ficient to bring about in a semiconductor an inversion of ener gy levels and provide for an amplification necessary for generation, scans across the surface of the semiconductor film. Thus excited, the semiconductor film is, in effect, the active medium of a laser.

Owing to the heating of the active region of the film at the depth of penetration of the electron beam, Coulomb interaction between nonequilibrium carriers, and lattice polarization,

- or the interaction of nonequilibrium carriers with phonons,

the wavelength of induced emission is greater than the limit of intrinsic absorption. Therefore, the unexcited regions of the film are transparent to the generated emission and do not produce appreciable losses in the resonator, even though the depth of penetration of the electrons in the semiconductor may be less than the thickness of the film. Feedback due to the reflection of light from the surfaces 7 and 8 of the plate 5 results in the generation of light in a direction normal to these surfaces.

In order to raise the Q-factor of the resonator, it is preferable to apply a reflecting coat (not shown in the drawing) to the surfaces 7 and 8 of the plate 5. The coat applied to the film surface exposed to the electron beam should be made fully reflecting, and that applied to the opposite side should be partly transmitting. Then the emission from the tube will be in the same direction as the electron beam, as is the casewith conventional cathode-ray tubes.

The directivity of emission can be enhanced by applying reflecting coats 9. and 10 (FIG. 2) to the surface 7 of the semiconductor plate 5 and to the external surface 11 of the substrate 6. In this embodiment the screen operates in a way similar to one described above and is, in effect, a semiconductor laser with an external reflector.

The directivity of emission may be improved still more by placing a semitransparent reflecting plate in front of the transparent substrate, on the outside of the evacuated envelope, said reflecting plate and the semiconductor film making up a resonator.

The screen shown in F IG'. 3 may be used in color television. It has a semiconductor film whose areas l2, l3 and 14 are made from different semiconductor materials emitting at different wavelengths. In this embodiment the cathode-ray tube has three electron guns (not shown in the HQ), and the electron beam from each gun is incident on the respective area on the screen. The separation of the electron beams may be accomplished by means of aperture masks, as in the conventional color television tubes.

The herein proposed cathode-ray tube increases the luminance of the screen about 1 ,000 times and has a short afterglow time, about lO- to l0- see, which fact makes it suitable for computer applications.

We claim:

1. A cathode-ray tube comprising, in combination, an evacuated envelope; an electron gun emitting a beam of electrons, a system for focusing and deflecting said beam of electrons; a screen on which said electron beam is focused for conversion of the energy of electrons into light energy, said screen being essentially a semiconductor quantum generator including an optical resonator and an active medium placed therein, said active medium being a film of semiconductor material deposited on a substrate and capable of induced light emission and amplification at the density of electrons in the beam sufficient to bring about an inversion of energy levels in said semiconductor film, one of the reflecting surfaces of the opti cal resonator being the surface of said film exposed to the electron beam inside the tube envelope.

2. A cathode-ray tube as defined in claim 1, wherein the substrate is made optically transparent, and the optical resonator is formed by the film surface exposed to the electron beam and a reflective coating deposited on a substrate outside the evacuated envelope.

3. A cathode-ray tube as defined in claim 1, wherein the film surface exposed to the electron beam has a thin dielectric coating which reflects the light emission.

4. A cathode-ray tube as defined in claim 1, wherein outside the evacuated tube envelope and parallel to the film surface there is placed a semitransparent reflector which forms, together with said film surface, the optical resonator.

5. A cathode-ray tube as defined in claim 1, wherein the substrate is optically nontransparent, and the resonator is formed by the film surface exposed to the electron beam and the fully reflective surface of the substrate, as a result of which the light emission from the screen radiates in the reverse direction relative to the direction of the electron beam.

6. A cathode-ray tube as defined in claim 1, wherein the film capable of induced light emission and amplification is of gallium arsenide.

7. A cathode-ray tube as defined in claim 1, wherein the film capable of induced light emission and amplification is of gallium arseno-phosphide.

8. A cathode-ray tube as defined in claim 1 wherein the film capable of induced light emission and amplification is of zinc selenide.

9. A cathode-ray tube as defined in claim 1, wherein the film capable of induced light emission and amplification is of cadmium selenide.

10. A cathode-ray tube as defined in claim 1, wherein the film capable of induced light emission and amplification is of cadmium sulfide.

11. A cathode-ray tube as defined in claim 1, wherein the film capable of induced light emission and amplification is of zinc sulfide. 

2. A cathode-ray tube as defined in claim 1, wherein the substrate is made optically transparent, and the optical resonator is formed by the film surface exposed to the electron beam and a reflective coating deposited on a substrate outside the evacuated envelope.
 3. A cathode-ray tube as defined in claim 1, wherein the film surface exposed to the electron beam has a thin dielectric coating which reflects the light emission.
 4. A cathode-ray tube as defined in claim 1, wherein outside the evacuated tube envelope and parallel to the film surface there is placed a semitransparent reflector which forms, together with said film surface, the optical resonator.
 5. A cathode-ray tube as defined in claim 1, wherein the substrate is optically nontransparent, and the resonator is formed by the film surface exposed to the electron beam and the fully reflective surface of the substrate, as a result of which the light emission from the screen radiates in the reverse direction relative to the direction of the electron beam.
 6. A cathode-ray tube as defined in claim 1, wherein the film capable of induced light emission and amplification is of gallium arsenide.
 7. A cathode-ray tube as defined in claim 1, wherein the film capable of induced light emission and amplification is of gallium arseno-phosphide.
 8. A cathode-ray tube as defined in claim 1, wherein the film capable of induced light emission and amplification is of zinc selenide.
 9. A cathode-ray tube as defined in claim 1, wherein the film capable of induced light emission and amplification is of cadmium selenide.
 10. A cathode-ray tube as defined in claim 1, wherein the film capable of induced light emission and amplification is of cadmium sulfide.
 11. A cathode-ray tube as defined in claim 1, wherein the film capable of induced light emission and amplification is of zinc sulfide. 